Field of the Invention
The present invention relates mainly to a turbine ventilation structure of a gas turbine engine which includes an exhaust diffuser having a sheet metal double structure.
Description of Related Art
As a structure of an exhaust diffuser that performs gas exhaustion from a turbine in a gas turbine engine, a double structure that includes an outer tube and an inner tube that are each made of a sheet metal is generally used (see, for example, Patent Document 1). A gas turbine engine including an exhaust diffuser having such a structure requires appropriate ventilation (cooling) for thermally protecting members, formed by casting, such as a support structural member and a bearing box inside the diffuser. When a sufficient negative pressure can be ensured at an exhaust diffuser inlet under any operating condition, ventilation can be performed by taking air for ventilation into the exhaust diffuser by using the negative pressure.
It has been suggested that, in the case where air for ventilation is taken into the exhaust diffuser by using the negative pressure at the exhaust diffuser inlet, a gap between a strut that supports a bearing of a turbine rotor and a strut cover that covers the strut is used as a passage of air for ventilation, thereby efficiently cooling the structure inside the diffuser (e.g., Patent Documents 2 and 3).